From memory, if you want to comment on the same line as script, you use two slashes, like this:
%HEALTH := %HEALTH + 5 // increasing health by 5
Like I said, that's from memory so I could be wrong. Try it out. Also I think the following works:
%HEALTH := %HEALTH + 5
/* this is a multi line
comment, in fact everything within
the slash-asterisk and asterisk-slash
is part of a comment and will be
ignored by the storygame engine */
%INTIMIDATE := 17